1. Field of the Invention
This invention relates to internal combustion engines and, more particularly, to internal combustion engines having means to adjust the compression ratios of the cylinders contained therein.
2. Description of the Related Art
Using variable compression ratio cylinders in an internal combustion engine to improve engine efficiency and reduce engine emissions are well known.
Several variable compression ratio cylinder designs are found in the prior art. For example, Prosen (U.S. Pat. No. 4,148,284) discloses a variable compression ratio engine with cylinders having inner and outer sleeves whose relative movement varies the cylinder volume to change the compression ratio of the engine. A complex hydraulic means responsive to the pressure in the combustion chamber automatically varies the position of the inner and outer sleeves to regulate the volume of the combustion chamber.
Coswell, Sr. (U.S. Pat. No. 4,137,873) discloses a variable compression ratio cylinder having a piston with a head portion with a flexible top wall located adjacent to the combustion chamber which flexes downward under high compression conditions to increase the volume of the combustion chamber.
Burnham (U.S. Pat. No. 4,046,116) discloses a means and method for increasing the compression ratio of the cylinder of an overhead valve engine by attaching plates having different thicknesses to the top face of the piston to reduce the volume of the combustion chamber.
The one disadvantage of these cylinder designs is that they require extensive modifications to the pistons or the cylinder heads. Another disadvantage is that they do not allow the mechanic to initially set and selectively control the amount of change in the volume of the combustion chamber during operation.